1. Field of the Invention
The present invention relates generally to medical devices and methods. More particularly, the present invention relates to catheters, systems, kits, and methods for treating ischemia, such as intracerebral ischemia associated with stroke.
Hemodynamically significant restriction of arterial blood flow can lead to oxygen deprivation in tissue, referred to as ischemia, and can quickly lead to cell death and organ dysfunction. The brain is the organ most sensitive to ischemia, followed by the heart, the abdominal organs, and the extremities. The brain will usually not tolerate ischemia for very long without massive neuron death (stroke). When treating ischemic events in the brain, it is imperative to restore blood flow quickly and safely.
The most common causes of acute arterial ischemia in the cerebrovasculature are thrombosis and embolus. Thrombus usually forms at the site of a pre-existing atherosclerotic lesion and can cause an acute occlusion. Atherosclerosis can occur at any location within the arteries that deliver blood from the heart to the brain, but the most common locations of significant atherosclerosis are the cervical carotid artery at the carotid bifurcation, the proximal middle cerebral artery, and the vertebrobasilar arterial system. Clinically significant atherosclerosis also can occur in other intracerebral vessels.
Emboli are formed when previously stable thrombus or atheroma is released into the blood stream and becomes lodged in smaller blood vessels. Emboli can originate from atherosclerotic lesions and from within the cardiac chambers. They can cause acute obstructions of blood vessels, resulting in tissue hypoxia and neuron death. Further obstruction can also occur distally to the embolus due to secondary inflammatory responses and other reactions. Transient ischemic attacks (TIA""s) occur with temporary and intermittent obstructions, allowing for neuron recovery. Stroke occurs with longer term obstruction to blood flow.
Acute arterial ischemia can also result from vasospasm, as a delayed response to intracranial hemorrhage, and may be iatrogenic, as when intracranial blood vessels are temporarily occluded during neurosurgery. Other causes include head trauma, inflammation, and infection.
Traditional therapy of acute stroke has been limited to the delivery of supportive measures. Newer treatments for stroke attempt to relieve or bypass vessel occlusion before neuron death occurs. In the life threatening emergency of acute stroke, there is a time-limited window of opportunity for treatment after the onset of symptoms. After this treatment window has closed, there is minimal opportunity for recovery of neuronal function. For all these reasons, physicians have emphasized the early treatment of patients, usually within six hours of the onset of symptoms, and on relieving the obstruction emergently.
When the obstruction is relieved, the ischemic bed will be exposed to normal arterial pressure. As will be discussed below, the inventor believes that reperfusion syndrome may result from prematurely exposing the previously ischemic bed to normal arterial pressure. Reperfusion syndrome may result from disordered function of the capillary endothelium and the blood-brain barrier in the previously ischemic vascular bed.
A number of techniques have been proposed which employ site-specific administration of thrombolytic drugs and/or mechanical means, laser or ultrasound energy sources to remove thrombus. Angioplasty, atherectomy and stent placement are employed to relieve atherosclerotic stenoses. These methods all require positioning catheter based devices at or near the site of the arterial obstruction. The primary objective is to restore blood flow as quickly as possible. Such devices, however, require significant time to position and use. There are also risks of damaging the obstructed artery, of dislodging and embolizing blood thrombus or atherosclerotic plaque, of inducing intracerebral hemorrhage or other serious complications. Directed thrombolysis using currently available catheters and guidewires often takes many hours to complete. While excellent technical results are feasible, many patients cannot tolerate the wait and their condition can deteriorate during the procedure. Moreover, the thrombolytic agents themselves may have deleterious biologic side effects. Surgical bypass does not work as well as standard medical therapy in preventing stroke recurrence and is only rarely performed.
New classes of xe2x80x9cneuroprotectantxe2x80x9d agents and xe2x80x9cangiogenesis promotersxe2x80x9d are being developed and tested. These drugs may extend the effective therapeutic window for stroke therapy and permit better long term outcomes. Their use, however, may require novel delivery systems and often require that the patient be stabilized and ischemia relieved in order to obtain a lasting clinical improvement.
For these reasons, it would be desirable to provide improved methods and apparatus for treating acute ischemic conditions, particularly stroke. It would be further desirable if such methods and apparatus were also useful for treating chronic ischemia in other portions of a patient""s vasculature, including the coronary vasculature and the peripheral and mesenteric vasculature. The methods and apparatus should be capable of rapidly reestablishing blood flow, at controlled pressures, at a rate sufficient to relieve ischemia distal to the occlusion, and may be adaptable for use in an emergency situation (i.e., outside the hospital) and/or within a hospital environment. The methods and apparatus should provide for control over the rate of flow, pressure in the ischemic bed and/or cessation of flow to the ischemic region in order to avoid reperfusion injury. In addition to relieving ischemia, the methods and devices of the present invention may also provide access and support for performing other therapeutic interventions to treat the occlusion, including both drug interventions and mechanical interventions. The methods and devices should be adaptable to use access routes of a type which are familiar to interventionalists so as to permit rapid and wide spread adoption. At least some of these objectives will be met by different aspects of the present invention.
2. Description of the Background Art
U.S. Pat. No. 5,149,321 describes an emergency system for infusing an oxygenated medium into the cerebral vasculature in patients following a heart attack. Active perfusion through coronary angioplasty catheters is described in a number of patents and published applications, including U.S. Pat. Nos. 5,106,363; 5,158,540; 5,186,713; and 5,407,424; Canadian Patent 1,322,315; and WO 97/19713. The latter describes perfusion of an oxygenated medium through a guidewire. Perfusion and/or infusion catheters and systems are described in a number of patents, including U.S. Pat. Nos. 5,584,804; 5,090,960; 4,611,094; 4,666,426; 4,921,483; 5,643,228; 5,451,207; 5,425,723; 5,462,523; 5,531,715; 5,403,274; 5,184,627; 5,066,282; 4,850,969; 4,804,358; 4,468,216; and WO 92/20398. U.S. Pat. No. 5,090,960 describes a passive perfusion catheter having spaced-apart balloons and a suction tube for recirculating a thrombolytic agent.
The present invention provides methods, apparatus, and kits for treating patients suffering from ischemia resulting from the partial or total obstruction of a blood vessel. Usually, the obstructions will be high-grade blockages, e.g., those which result in greater than 75% flow reduction, but in some instances they may be of a lower grade, e.g., ulcerated lesions. As used hereinafter, the terms xe2x80x9cobstruction,xe2x80x9d xe2x80x9cocclusion,xe2x80x9d and xe2x80x9cblockagexe2x80x9d will be used generally interchangeably and will refer to both total obstructions where substantially all flow through a blood vessel is stopped as well as to partial obstructions where flow through the blood vessel remains, although at a lower rate than if the obstruction were absent.
Preferred use of the present invention is for the treatment of patients suffering from acute stroke resulting from a sudden, catastrophic blockage of a cerebral artery. The invention may also be used to minimize or prevent ischemia during other conditions which result in blocked points or segments in the cerebral arterial vasculature, such as iatrogenic occlusion of an artery, e.g., during neurosurgery, or to relieve vasospasm induced ischemia. The present invention, however, will also be useful for treating acute blockages in other portions of the vasculature as well as for treating chronic occlusions in the cerebral, cardiac, peripheral, mesenteric, and other vasculature. Optionally, the methods of the present invention may be used to facilitate dissolving or removing the primary obstruction responsible for the ischemia, e.g., by drug delivery, mechanical intervention, or the like, while perfusion is maintained to relieve the ischemia.
Methods according to the present invention comprise penetrating a perfusion conduit through the blockage and subsequently pumping an oxygenated medium through the conduit at a rate or pressure sufficient to relieve ischemia downstream from the blockage. The oxygenated medium is preferably blood taken from the patient being treated. In some instances, however, it will be possible to use other oxygenated media, such as perfluorocarbons or other synthetic blood substitutes. In a preferred aspect of the present invention, the pumping step comprises drawing oxygenated blood from the patient, and pumping the blood back through the conduit at a controlled pressure and/or rate, typically a pressure within the range from 50 mmHg to 400 mmHg, preferably at a mean arterial pressure in the range from 50 mmHg to 150 mmHg, and at a rate in the range from 30 cc/min to 360 cc/min, usually from 30 cc/min to 240 cc/min, and preferably from 30 cc/min to 180 cc/min, for the cerebral vasculature. Usually, pressure and flow rate will both be monitored. The blood flow system preferably keeps the pressure at or below 400 mmHg, 350 mmHg, or 300 mmHg. Pressure is preferably monitored using one or more pressure sensing element(s) on the catheter which may be disposed distal and/or proximal to the obstruction where the blood or other oxygenated medium is being released. Flow rate may easily be monitored on the pumping unit in a conventional manner or may be monitored by a separate control unit. Conveniently, the blood may be withdrawn through a sheath which is used for percutaneously introducing the perfusion conduit.
It will usually be desirable to control the pressure and/or flow rate of the oxygenated medium being delivered distally to the occlusion. Usually, the delivered pressure of the oxygenated medium should be maintained below the local peak systolic pressure and/or mean arterial blood pressure of the vasculature at a location proximal to the occlusion. It will generally be undesirable to expose the vasculature distal to the occlusion to a pressure above that to which it has been exposed prior to the occlusion. Pressure control of the delivered oxygenated medium will, of course, depend on the manner in which the medium is being delivered. In instances where the oxygenated medium is blood which is being passively perfused past the occlusion, the delivered pressure will be limited to well below the inlet pressure, which is typically the local pressure in the artery immediately proximal to the occlusion. Pressure control may be necessary, however, when the oxygenated medium or blood is being actively pumped. In such cases, the pump may have a generally continuous (non-pulsatile) output or in some cases may have a pulsatile output, e.g., being pulsed to mimic coronary output. In the case of a continuous pump output, it is preferred that the pressure in the vascular bed immediately distal to the occlusion be maintained below the mean arterial pressure usually being below 150 mmHg, often being below 100 mmHg. In the case of a pulsatile pump output, the peak pressure should be maintained below the peak systolic pressure upstream of the occlusion, typically being below 200 mmHg, usually being below 150 mmHg.
Pressure control of the oxygenated medium being delivered downstream of the occlusion is preferably achieved using a digital or analog feedback control apparatus where the pressure and/or flow output of the pump is regulated based on a measured pressure and/or flow value. The pressure value may be measured directly or indirectly. For example, the pressure downstream of the occlusion may be measured indirectly through the perfusion conduit. A separate pressure lumen may be provided in the perfusion conduit and a pressure measurement transducer located at the proximal end of the conduit. Pressure sensed by a distal port of the pressure measuring conduit will then be transmitted through the conduit to the transducer. Pressure transducers are a preferred pressure sensor for measuring pressure in the vasculature distal to the occlusion. The pressure sensors may be mounted near the distal tip of the perfusion conduit itself or could be mounted on a separate guidewire or other structure which crosses the occlusion with the perfusion conduit. The pressure signals generated by the transducers are transmitted through electrically conductive elements, such as wires, to the proximal end of the perfusion conduit where they are connected to a pressure monitor connected to or integral with the controller. The pump output can then be controlled based on conventional control algorithms, such as proportional control algorithms, derivative control algorithms, integral control algorithms, or combinations thereof. In one embodiment of the present invention, the pressure sensor is spaced from the perfusion outlets so that fluid flow forces do not affect the pressure measurements.
Actual manipulation of the pressure and/or flow provided by a circulating pump can be effected in a variety of ways. In the case of centrifugal pumps, the flow can be measured at the pump output and the pressure can be measured in any of the ways set forth above. Control of both the flow rate and the pressure can be achieved by appropriately changing the pump speed and downstream flow resistance, where the latter can be manipulated using a control valve. Suitable flow control algorithms are well described in the patent and technical literature.
Control of peristaltic and other positive displacement pumps is achieved in a slightly different way. Flow volume from a positive displacement pump is a linear function of the pump speed and thus may be controlled simply by varying the pump speed. Pressure output from the positive displacement pump, in contrast, will be dependent on flow resistance downstream from the pump. In order to provide for control of the output pressure from the pump (which is necessary to control the pressure downstream of the occlusion), a pressure control system may be provided. Typically, the pressure control system may comprise a by-pass flow loop from the pump output back to the pump inlet. By then controlling the amount of blood output which is by-passed back to the inlet, that pressure can be manipulated. Typically, a flow control valve can be used to adjust the by-pass flow in order to achieve the target pressure control point downstream of the obstruction. Suitable flow and pressure control algorithms for positive displacement pumps, such as roller pumps, are well described in the patent and technical literature.
In addition to controlling pressure and/or flow rates, the systems of the present invention can provide control for a number of other parameters, such as partial oxygen pressure (pO2) in the perfused blood, partial carbon dioxide pressure (pCO2) in the perfused blood, pH in the perfused blood, temperature of the perfused blood, metabolite concentrations, and the like. Both pO2 and pCO2 can be controlled using the oxygenator in the system, as described in more detail below. The pH can be controlled by introducing appropriate physiologically acceptable pH modifier(s), such as buffer and bicarbonate solutions and the like. Temperature is controlled by providing appropriate heat exchange capabilities in the extracorporeal pumping system. The temperature will usually be decreased in order to further inhibit tissue damage from the ischemic conditions, but could be elevated for other purposes. Suitable sensors and devices for measuring each of the parameters are commercially available, and suitable control systems can be provided as separate analog units or as part of a digital controller for the entire system, such as a desk or lap top computer which is specially programmed to handle the monitoring and control functions as described in this application. Concentration and/or physiologic activity of certain formed cellular elements, such as white blood cell or platelets, can be selectively controlled with suitable control systems and devices
A particular advantage of the present invention lies in the ability to lessen or eliminate reperfusion injury which can result from the rapid restoration of full blood flow and pressure to ischemic tissue. As described above, the use of thrombolytics and other prior treatments can cause the abrupt removal of an obstruction causing rapid infusion of blood into the ischemic tissue downstream of the occlusion. It is believed that such rapid restoration of full blood flow and pressure, typically at normal physiologic pressures, can result in further damage to the leaky capillary beds and dysfunctional blood-brain barrier which results from the prior ischemic condition.
The present invention allows for a controlled reperfusion of the ischemic tissue where blood can initially be released downstream of the obstruction at relatively low pressures and/or flow rates. That is, it will be desirable to initiate the flow of blood or other oxygenated medium slowly and allow the flow rate and pressure to achieve their target values over time. For example, when actively pumping the oxygenated medium, the pumping rate can be initiated at a very low level, typically less than 30 cc/min, often less than 10 cc/min, and sometimes beginning at essentially no flow and can then be increased in a linear or non-linear manner until reaching the target value. Rates of increase can be from 1 cc/min/min to 360 cc/min/min, usually being from 5 cc/min/min to 120 cc/min/min. Alternatively, the flow of blood or other oxygenated medium can be regulated based on pressure as mentioned above. For example, flow can begin with a pressure in the previously ischemic bed no greater than 10 mmHg, typically from 10 mmHg to 70 mmHg. The pressure can then be gradually increased, typically at a rate in the range from 5-100 mmHg over 2, 8 or even 48 hours. In some instances, it may be desirable to employ blood or other oxygenated medium that has been superoxygenated, i.e., carrying more oxygen per ml than normally oxygenated blood.
While pumping will usually be required to achieve and/or maintain adequate perfusion, in some instances passive perfusion may be sufficient. In particular, perfusion of the smaller arteries within the cerebral vasculature can sometimes be provided using a perfusion conduit having inlet ports or apertures on a proximal portion of the conduit and outlet ports or apertures on a distal portion of the conduit. By then positioning the inlet and outlet ports on the proximal and distal sides of the obstruction, respectively, the natural pressure differential in the vasculature will be sufficient to perfuse blood through the conduit lumen past the obstruction. Usually, the inlet ports on the perfusion conduit will be located at a location as close to the proximal side of the occlusion as possible in order to minimize the length of perfusion lumen through which the blood will have to flow. In some instances, however, it may be necessary to position the inlet ports sufficiently proximal to the occlusion so that they lie in a relatively patent arterial lumen to supply the necessary blood flow and pressure. The cross-sectional area of the perfusion lumen will be maintained as large as possible from the point of the inlet ports to the outlet ports. In this way, flow resistance is minimized and flow rate maximized to take full advantage of the natural pressure differential which exists.
While perfusion is maintained through the perfusion conduit, treatment of the blood vessel blockage may be effected in a variety of ways. For example, thrombolytic, anticoagulant and/or anti-restenotic agents, such as tissue plasminogen activator (tPA), streptokinase, urokinase, heparin, or the like, may be administered to the patient locally (usually through the perfusion catheter) or systemically. In a preferred aspect of the present invention, such thrombolytic and/or anticoagulant agents may be administered locally to the arterial blockage, preferably through a lumen in the perfusion catheter itself. Such local administration can be directly into the thrombus, e.g., through side infusion ports which are positioned within the thrombus while the perfusion port(s) are positioned distal to the thrombus. Optionally, a portion of the blood which is being perfused could be added back to or otherwise combined with thrombolytic and/or anticoagulant agent(s) being administered through the catheter. The addition of blood to certain thrombolytic agents will act to catalyze the desired thrombolytic activity. The availability of the patient blood being perfused greatly facilitates such addition. It would also be possible to deliver the agent(s) through the same lumen and distal port(s) as the blood being pumped back through the perfusion lumen so that the agents are delivered distally of the catheter. The latter situation may be used advantageously with neuroprotective agents, vasodilators, antispasmotic drugs, angiogenesis promoters, as well as thrombolytics, anticoagulants, and anti-restenotic agents, and the like. The two approaches, of course, may be combined so that one or more agents, such as thrombolytic agents, are delivered directly into the thrombus while neuroprotective or other agents are delivered distally to the thrombus. Moreover, such delivery routes can also be employed simultaneously with systemic delivery of drugs or other agents to the patient.
Alternatively or additionally, mechanical interventions may be performed while the vasculature is being perfused according to the present invention. For example, a perfusion conduit may have a very low profile and be used as a guide element to introduce an interventional catheter, such as an angioplasty catheter, an atherectomy catheter, a stent-placement catheter, thrombus dissolution device, or the like.
The perfusion of the oxygenated medium may be performed for a relatively short time in order to relieve ischemia (which may be advantageous because of damaged capillaries and/or blood-brain barrier) while other interventional steps are being taken, or may be performed for a much longer time either in anticipation of other interventional steps and/or while other long-term interventions are being performed. In particular, when thrombolytic and/or anticoagulant agents are being used to treat the primary blockage, the perfusion can be continued until the blockage is substantially relieved, typically for at least thirty minutes, often for four to eight hours, or even 2-3 days. In other instances, perfusion can be maintained for much longer periods, e.g., more than one week, more than two weeks, more than a month, or even longer. In some cases, it may even be desirable to maintain perfusion and placement of the perfusion conduit for an extended period of time with the patient having a portable or implantable pump coupled to the conduit. The pump may also have a reservoir for delivery of therapeutic agents and may be implanted or carried on a belt or the like.
The ability of the present invention to provide for gradual or controlled restoration of physiologic blood perfusion pressures and flow rates is a particular advantage when subsequent interventional steps would otherwise result in abrupt restoration of blood flow. As described above, abrupt restoration of blood flow can cause or contribute to reperfusion injuries. By providing for controlled restoration of blood flow prior to such interventional steps, the ischemic tissue can be conditioned to tolerate physiologic blood flow rates and pressures prior to full restoration by dissolution or other removal of the occlusion. Such gradual restoration of blood flow from very low levels to physiologic flow rates can typically be achieved over time periods in the range from one minute, an hour or even up to 48 hours or longer. Perfusion at controlled pressure and/or flow rate may last typically in the range of 30 minutes to 2 hours, more typically 30 minutes to 9 hours. It will be desirable, for example, to initiate perfusion through the perfusion conduits of the present invention at mean arterial pressures downstream of the occlusion which are no greater than 25-50% of normal with typical pressures being 20-40 mmHg. The blood flow rates which correspond to such pressures will depend largely on the nature of the vasculature into which the blood is being perfused and may be less than 200 ml/min, less than 150 ml/min and even less than 100 ml/min.
In addition to delivering oxygen to the ischemic region distal to the primary occlusion, the blood or other oxygenated medium may carry other treatment agents, including thrombolytic agents, anticoagulant agents, tissue preservative agents, and the like. Moreover, in order to further preserve the cerebral tissue distal to the blockage, the oxygenated medium may be cooled to below body temperature, e.g., to a temperature in the range from 2xc2x0 C. to 36xc2x0 C., typically from 25xc2x0 C., to 36xc2x0 C., in order to cool and preserve the tissue. Cooling may be effected externally as part of the extracorporeal pumping system and/or may be effected using a thermoelectric or Joule-Thomson expansion cooler on the catheter itself.
Patients suffering from ischemia resulting from acute or chronic occlusion in the cerebral vasculature may be treated according to the preferred methods described below. A perfusion conduit is introduced to the patient""s vasculature, and a distal port on the conduit is guided through the occlusion in the cerebral vasculature. Blood, optionally oxygenated and/or superoxygenated, is obtained from the patient and perfused back to the patient through the distal port on the conduit past the occlusion at a rate sufficient to relieve the ischemia. The oxygenated blood may be arterial blood which may be returned to the patient without further oxygenation. Alternatively, arterial or venous blood can be oxygenated in suitable apparatus external to the patient and returned to the patient. External oxygenation allows the blood to be xe2x80x9csuperoxygenated,xe2x80x9d i.e., oxygenated at higher levels than would normally be available from arterial blood. Usually, the method further comprises delivering a therapeutic agent to the patient while the perfusing step is continued, usually being a thrombolytic agent which is delivered through the conduit directly to the vascular occlusion. The occlusion is usually in either a carotid artery, vertebral artery, proximal subclavian artery, brachiocephalic artery, or an intracerebral artery, and the conduit is usually introduced via the femoral artery in a conventional intravascular approach, typically being positioned over a guidewire which is first used to cross the occlusion. Alternatively, the conduit may be introduced through the axillary or brachial arteries, also in a conventional manner.
Apparatus according to the present invention comprises perfusion/infusion catheters which include a catheter body having a proximal end and a distal end. The catheter body has at least a perfusion lumen and may have other lumens. The catheter may be tapered or may have a constant cross-sectional shape. The catheter may be formed as a single, multi-lumen or single-lumen extrusion or the lumens may be formed as separate tubes. When formed as separate tubes, the tubes may be fixed relative to each other or may be provided with appropriate sliding seals to permit them to slide relative to each other. Additional lumens and/or tubes may also be provided for purposes discussed in more detail below. Often, although not always, the catheters will be free from external dilatation balloons or other external structure which could complicate penetration of the distal end of the catheter through an obstruction.
A first embodiment of the catheter is characterized by a large diameter proximal section and a small diameter distal section, where at least two isolated lumens extend from the proximal end of the catheter body through both sections to near the distal end of the catheter body. One of the lumens will extend entirely through the catheter body and usually have side ports over a distal length thereof. The other lumen will usually terminate some distance proximal of the distal tip of the catheter body and will also usually have side ports over a distal length thereof. The proximal section has an outer diameter in the range from 1 mm to 3 mm, usually from 1.5 mm to 2.5 mm, and typically from 1.5 mm to 2 mm, and the distal section has an outer diameter in the range from 0.5 mm to 2 mm, preferably from 0.5 mm to 1.5 mm. The first isolated lumen which extends entirely through the catheter body will usually be tapered, i.e., have a larger diameter over a proximal length thereof than over a distal length thereof. Usually, the first isolated lumen will have an inner diameter in the range from 0.75 mm to 1.25 mm in the proximal section, more usually being from 0.9 mm to 1.1 mm in the proximal section, and an inner diameter in the range from 0.25 mm to 1 mm in the distal section, usually being from 0.3 mm to 0.75 mm in the distal section. The second isolated lumen will usually be disposed annularly about the first isolated lumen and will have an inner diameter in the range from 0.9 mm to 2.9 mm in the proximal section, usually from 1.4 mm to 1.9 mm in the proximal section, and an inner diameter in the range from 0.4 mm to 1.9 mm in the distal section, usually in the range from 0.5 mm to 1.5 mm in the distal section. The second, outer annular lumen will typically terminate from 5 cm to 25 cm from the distal end of the catheter body.
The catheter may also have a larger flow conduit for achieving higher flow rates. For example, the inner diameter of the first lumen may be 1.5-3.0 mm in the proximal section and 1.0-2.0 mm in the distal section. The second lumen has an inner diameter which is preferably 0.25-1.0 mm larger than the outer diameter of the first lumen. The wall thickness of the first lumen is preferably between 0.07-0.20 mm. If the catheter has a straight instead of tapered configuration the inner diameter of the first lumen is preferably 1.5-2.5 mm.
The catheter of the present invention may, of course, have any other suitable tapered shape or may have a constant cross-sectional profile. For example, in another preferred embodiment, the first catheter has the perfusion lumen, and in a specific embodiment no other fluid lumens. Such a catheter has a small, flexible construction which can be passed through tortuous vessels. Other catheters may be advanced over the perfusion catheter to remove or displace the obstruction as discussed below. The catheters may be another fluid perfusion catheter for delivery of thrombolytic agents or may be an obstruction removal catheter which removes the obstruction with mechanical action or with an ultrasound transducer, RF electrode or a laser.
In another aspect of the present invention, the perfusion conduit is advanced through the cerebral vasculature to the obstruction and an obstruction removal catheter is advanced through the perfusion lumen to remove the obstruction. Thus, the perfusion conduit acts as a fluid conduit and/or a guide catheter for reaching distal regions of the cerebral vasculature. The system of the present invention permits the introduction of catheters through the perfusion lumen to regions as distal as the middle cerebral artery M1 and M2 segments, anterior cerebral artery A1 and A2 segments, and the basilar artery or other similarly sized vessels which are typically accessed with guidewires. The obstruction removal catheter may be a balloon, stent, perfusion, RF, ultrasound, laser or mechanical atherectomy catheter for removing the obstruction.
The present invention is also directed to a system having a balloon catheter and an infusion catheter. The balloon catheter has at least one lumen extending therethrough. The second catheter has a guide tip and fluid infusion openings in a distal region. Both catheters have a proximal region which has a cross-sectional area greater than the distal region. The second catheter is slidably received in the first catheter so that the guide tip and the fluid infusion openings can extend distally from the first catheter.
In another method of the present invention, a method of performing balloon displacement of an obstruction in a patient""s vasculature is provided. A balloon catheter is guided over a guidewire to a site in a patient""s vasculature. The guidewire is then removed. An infusion catheter is then introduced through the balloon catheter. The infusion catheter is advanced through the balloon catheter so that the tip extends beyond the balloon catheter. An infusate is then delivered through the infusion catheter.
In still another aspect of the present invention, a balloon catheter is provided which is configured to be guided through the perfusion catheter. The balloon catheter has no guidewire lumen and no other structure to track over a guidewire thereby reducing the size of the catheter. The distal end of the balloon catheter preferably has a smooth, rounded tip to penetrate the obstruction if necessary. The balloon catheter may have a tapered shape similar to the perfusion catheter.
Apparatus according to the present invention further comprises systems including a perfusion/infusion catheter as set forth above in combination with a sheath for percutaneously introducing the perfusion/infusion catheter and a pump for receiving blood from the sheath and delivering blood back to the catheter. Optionally, an infusion device may be provided in the system for infusing a drug to a lumen of the perfusion/infusion catheter. Preferably, the systems will include control apparatus for controlling blood infusion pressures, blood infusion flow rates, pO2, pCO2, pH, temperature, and/or other parameters of the blood/oxygenated medium being perfused back to the patient. The present invention still further comprises kits, including a perfusion catheter and instructions for use setting forth a method for penetrating the catheter through a blockage in a patient""s vasculature and thereafter perfusing an oxygenated medium through the conduit to relieve ischemia. Kits will usually further comprise a container, such as a pouch, tray, box, tube, or the like, which contains the catheter as well as the instructions for use. Optionally, the instructions for use set forth on a separate instructional sheet within the package, but alternatively could be printed in whole or in part on the packaging itself. Optionally, other system components useful for performing the methods of the present invention could be provided within the kit, including guidewires, introductory sheaths, guiding catheters, and the like.